Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/42—Platinum
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
  • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/44—Palladium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/18—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the mordenite type
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/19—Catalysts containing parts with different compositions
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0244—Coatings comprising several layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0246—Coatings comprising a zeolite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0248—Coatings comprising impregnated particles
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
  • F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
  • F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filter
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
  • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
  • F01N3/0835—Hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/206—Rare earth metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20738—Iron
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20761—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/50—Zeolites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/912—HC-storage component incorporated in the catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/915—Catalyst supported on particulate filters
  • B01D2255/9155—Wall flow filters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
  • B01J29/10—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y containing iron group metals, noble metals or copper
  • B01J29/12—Noble metals
  • B01J29/126—Y-type faujasite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/74—Noble metals
  • B01J29/7415—Zeolite Beta
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/80—Mixtures of different zeolites
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2370/00—Selection of materials for exhaust purification
  • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2370/00—Selection of materials for exhaust purification
  • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
  • F01N2370/04—Zeolitic material
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2510/00—Surface coverings
  • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
  • F01N2510/063—Surface coverings for exhaust purification, e.g. catalytic reaction zeolites
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2510/00—Surface coverings
  • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
  • F01N2510/068—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings
  • F01N2510/0682—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S502/00—Catalyst, solid sorbent, or support therefor: product or process of making
  • Y10S502/514—Process applicable either to preparing or to regenerating or to rehabilitating catalyst or sorbent

Definitions

• the invention relates to a catalytically coated diesel particulate filter for cleaning the exhaust gases of diesel engines, to a process for coating the filter and to the use thereof.
• Particulate filters are capable of filtering particulate exhaust gas constituents, particularly soot particles, out of the exhaust gas of internal combustion engines, thus preventing their emission into the atmosphere.
• surface filters consist typically of ceramic materials, for example silicon carbide, cordierite, aluminum titanate or mullite. These filters achieve filtration levels of more than 95%.
• open structures for deposition of soot particles. These open structures are primarily ceramic foams or filters composed of metallic wire braids. The filtration efficiency of these open filter systems is much lower than that of typical surface filters ( ⁇ 70%).
• the filters were usually arranged after one or two upstream oxidation catalysts in the underbody of the motor vehicle.
• the filters In new exhaust gas aftertreatment systems, the filters, in contrast, are installed as close as possible downstream of the engine. Owing to the restricted construction space and to reduce costs, the oxidation catalyst in these cases is applied partially or completely to the filter.
• Such a filter arranged close to the engine must, to comply with the legal limits for carbon monoxide (CO) and hydrocarbons (HC) over the required distance traveled, possess a correspondingly high oxidation potential.
• the catalytically active coating for use of such a filter close to the engine must have a high thermal stability.
• the noble metal sites of the catalytic coating are simultaneously desulfated during the regenerations in the case of periodically actively regenerating systems, for example in the case of diesel particulate filters. This re-establishes the original oxidation activity.
• WO 02/26379 A1 describes, among other things, a soot filter which comprises two catalyst layers one on top of another.
• the first layer is present on the inlet channels of the filter and comprises components for oxidizing carbon monoxide and hydrocarbons. These components consist of support materials with platinum group metals deposited thereon, the support materials being selected from the group consisting of aluminum oxide, silicon oxide, titanium oxide, zirconium oxide and zeolite, and the platinum group metals being selected from platinum, palladium and rhodium.
• the second layer is applied to the first layer and comprises components for lowering the ignition temperature of soot, more particularly at least one oxygen-storing compound and at least one platinum group metal.
• the particulate filter has an entry side and an exit side for the exhaust gases and an axial length.
• the filter is coated over its entire length with a first catalyst which comprises platinum group metals as catalytically active components on support materials.
• the filter is characterized in that the support materials for the platinum group metals are selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, cerium oxide and mixtures or mixed oxides thereof, and in that the first catalyst additionally comprises at least one zeolite for storage of hydrocarbons.
• the particulate filter is coated with a second catalyst which does not comprise a zeolite over a fraction of the length proceeding from the entry side.
• the zeolites used for the first catalyst preferably have a modulus (molar SiO 2 to Al 2 O 3 ratio) of more than 10 in order to be sufficiently stable toward the acidic components of the exhaust gas and the maximum exhaust gas temperatures.
• Suitable zeolites are, for example, mordenite, silicalite, Y zeolite, ZSM-5 zeolite and beta zeolite or mixtures thereof, said zeolites having a molar ratio of silicon dioxide to aluminum oxide between 10 and 400.
• the zeolites store the hydrocarbons present in the exhaust gas. This is important since oxidation of the hydrocarbons at the active noble metal sites of the catalyst is impossible at these low exhaust gas temperatures. In modern passenger vehicle diesel engines, such operating phases occur both during a cold start and during idling phases, and also in urban traffic. At temperatures above about 200° C., in contrast, the desorption of the hydrocarbons predominates. At these higher catalyst temperatures, however, the hydrocarbons released from the storage components can be converted over the active sites of the catalyst to carbon dioxide and water.
• the zeolites may additionally be catalytically activated with platinum group metals (platinum, palladium, rhodium, iridium) or with transition metals (for example, iron, copper, cerium).
• platinum group metals platinum, palladium, rhodium, iridium
• transition metals for example, iron, copper, cerium
• the zeolites can be impregnated, for example, with aqueous solutions of soluble precursor compounds. After the impregnation, the zeolites are dried, calcined and optionally reduced.
• the noble metal loading on the zeolite is preferably between 0.1 and 10% by weight, based on the total weight of zeolites and platinum group metals.
• the zeolites in the ammonium or sodium form are doped by ion exchange with the transition metals.
• the ion exchange can be carried out either in solution or as a so-called solid state ion exchange.
• the loading with transition metals is preferably approx. 1 to 15% by weight based on the total weight.
• the first catalyst comprises at least one platinum group metal or a plurality thereof, preferably a combination of platinum and palladium with a weight ratio of platinum to palladium of 1:10 to 20:1, preferably of 1:1 to 10:1, especially 2:1.
• Suitable support materials for the platinum group metals are aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, cerium oxide and mixtures or mixed oxides thereof.
• the support materials can be thermally stabilized by doping with rare earth oxides, alkaline earth metal oxides or silicon dioxide.
• doping with barium oxide, lanthanum oxide or silicon dioxide can increase the conversion temperature of ⁇ - to ⁇ -aluminum oxide from approx. 950 up to 1100° C.
• the concentration of the doping elements is typically 1 to 40% by weight.
• cerium oxide as the support material, it is advantageous to use cerium/zirconium mixed oxides, since these generally possess a higher thermal stability than the pure cerium oxide.
• the stability of the cerium/zirconium mixed oxides can be improved further by doping with praseodymium oxide or neodymium oxide.
• cerium/zirconium mixed oxides also possess advantageous oxygen storage properties, with regard both to the maximum oxygen storage capacity and to the kinetics of oxygen storage and release.
• the particulate filter is coated with the second catalyst over a fraction of its length proceeding from the entry side.
• This second catalyst may be identical to or else different from the first catalyst, both with regard to the catalytically active noble metals and with regard to the support materials used. Preference is given to using, for the additional coating, a catalyst with the same composition as the first catalyst. However, the second catalyst does not comprise any zeolites.
• the length of the second catalyst may be 5 to 80% of the total length of the filter substrate, preferably 10 to 50%.
• a portion of the noble metal would contribute only to a small degree or even not at all to the conversion of carbon monoxide and hydrocarbons.
• the noble metal concentration should not be below a minimum of approx. 0.1 g/l on the filter outlet side, since there is otherwise the risk of so-called secondary emissions, i.e. breakthroughs of carbon monoxide and hydrocarbons, in the case of active filter regenerations.
• solid powder materials these are suspended, for example, in water and ground for the purpose of homogenization and establishment of a defined particle size distribution.
• the grinding is performed such that the maximum particle size in the suspension is less than 10 ⁇ m. This is generally the case when the d 50 diameter is less than 2 ⁇ m. Only this small particle size allows the catalyst to be deposited virtually exclusively in the pores of the substrate.
• the support materials used in the suspension are typically already activated with platinum group elements before they are introduced into the suspension. However, it is also possible only to add dissolved precursor compounds of the catalytically active platinum group metals to the suspension of the support materials. In addition, it is also possible, after application of the support materials to the filter substrate, to subsequently impregnate the filter with soluble precursors of the platinum group metals.
• the particle diameters should preferably be established separately by grinding for catalyst materials and zeolites.
• Catalyst materials and zeolites have different hardnesses. Only by separate grinding for both materials can a comparable particle size distribution be guaranteed. Therefore, for the coating of the filter, two separate suspensions are first made up.
• the first suspension comprises the support materials which are activated with noble metals (for example platinum, palladium).
• the second suspension comprises the zeolites.
• the zeolites are preferably doped in a preceding process step by impregnation or ion exchange with noble metal. However, it is also possible to add noble metal to the zeolite suspension with the aid of suitable precursor compounds.
• a mean particle diameter d 50 less than 2 ⁇ m is then established separately by grinding; the d 90 value should be not more than 5-6 ⁇ m.
• the two suspensions are mixed and homogenized.
• Both the first and the second catalyst may comprise zeolites.
• the first catalyst comprises zeolites.
• the second catalyst then serves only to increase the concentration of the catalytically active noble metals in the front part of the particulate filter.
• the axial temperature profile in the filter which is highly pronounced in the case of filter substrates composed of silicon carbide, can be exploited optimally.
• the distribution of the zeolites between the first and second catalysts influences the development of the exhaust gas backpressure of the coated filters.
• the backpressure is significantly higher than when the zeolites are coated homogeneously with the first catalyst over the entire length of the filter.
• the use of zeolites in the first and second catalysts showed no significant difference in backpressure behavior with equal overall loading of zeolites compared to the exclusive arrangement of the zeolites in the first catalyst.
• the storage capacity for hydrocarbons increases with rising amount of zeolites.
• the maximum usable amount of zeolites depends significantly on the porosity and the mean pore diameter of the filter substrate used.
• Typical zeolite loadings range from 5 g/l (filter volume) in the case of low-porosity substrates ( ⁇ 50%) to approx. 50 g/l in the case of substrates with relatively high porosity (>50%).
• the ratio of zeolites to the support materials doped with noble metal in the inventive particulate filters is preferably 0.1 to 10.
• the known filter substrates are suitable for the diesel particulate filters. Preference is given to using so-called wall flow filters composed of silicon carbide, cordierite, aluminum titanate or mullite.
• the material of the filters should possess an open-pore structure with a porosity between 40 and 80% and a mean pore diameter between 9 and 30 ⁇ m.
• the substrates used were in each case a filter composed of silicon carbide with a cell density of 46.5 cm ⁇ 1 (300 cpsi) and a thickness of the channel walls of 0.3 mm (12 mil).
• the porosity of the filter material used was 60%; the mean pore diameter was 20 ⁇ m.
• the filter bodies had a length of 152.4 mm.
• the backpressure of three particulate filters laden differently with support oxides and zeolites was measured in a backpressure apparatus at flow rates between 150 and 300 m 3 /h.
• Filter 1 was unladen.
• Filter 2 received a coating with an aluminum oxide suspension which, after drying and calcination, had a loading concentration of about 30 g/l.
• Filter 3 was coated with aluminum oxide and with a zeolite mixture of a Y zeolite and a beta zeolite (mixing ratio 1:1).
• Aluminum oxide and zeolites were, in accordance with the invention, ground separately until the mean particle size of aluminum oxide and of the zeolites was less than 2 ⁇ m.
• the loading of filter 3 was 30 g/l of aluminum oxide and 10 g/l of the zeolite mixture.
• a filter substrate was first coated homogeneously over the entire filter length with a Pt/Pd catalyst supported on a stabilized ⁇ -aluminum oxide.
• the coating suspension was ground until a mean particle diameter of less than 2 ⁇ m had been attained.
• the coating step deposited the catalyst material almost completely into the pores of the filter substrate.
• the Pt/Pd ratio of this first catalyst layer was 2:1 and the noble metal loading was 2.12 g/l (60 g/ft 3 ).
• a second catalyst layer with a noble metal content of likewise 2.12 g/l (60 g/ft 3 ) and identical Pt/Pd ratio was applied over half of the filter length.
• the resulting total noble metal loading of the comparative filter C was thus approx. 90 g/ft 3 , or 3.18 g/l.
• the second catalyst layer was also intercalated predominantly into the pores of the filter substrate.
• a second filter substrate was coated with the inventive catalyst.
• the filter was first coated homogeneously over the entire filter length with a noble metal loading of 60 g/ft 3 .
• the inventive coating contained, in addition to the ⁇ -aluminum oxide stabilized with Pt/Pd in a ratio of 2:1, also a zeolite mixture composed of a Y zeolite and a beta zeolite (mixing ratio 1:1). Before being added to the coating suspension, both zeolites were doped with small amounts of Pt (0.5% by weight) by means of impregnation. The ratio of ⁇ -aluminum oxide to zeolite mixture was approx. 1:1.
• the entry side of the filter was coated with an additional 2.12 g/l of noble metal using the identical coating suspension.
• the total concentration of the noble metals Pt and Pd on the filter F1 was thus 3.18 g/l (90 g/ft 3 ) at a Pt/Pd ratio of 2:1.
• the testing of the catalytic activity of the two filters was carried out in the fresh state and after a hydrothermal furnace aging on a EURO IV certified passenger vehicle with a 103 kW 2.01 diesel engine with pump-nozzle injection system.
• the filters were arranged close to the engine and were analyzed without an upstream diesel oxidation catalyst in the NEDC (New European Driving Cycle) test cycle.
• the results including the untreated emissions of the vehicle are compiled in table 1.
• filter F1 Analogously to example 1 (filter F1), two further filter substrates were coated with a noble metal loading of 3.18 g/l. In the filter F2, in contrast to the filter F1, the amount of zeolite of 20 g/l was applied over the entire filter length exclusively in the first catalyst layer. In filter F3, the zeolites were applied exclusively with the second catalyst layer.
• the zeolites used were, as in example 1, a mixture of a Y zeolite and a beta zeolite (mixing ratio 1:1). The two zeolites used had each been doped with 0.5% by weight of Pt.
• the catalytic activity of the filters F2 and F3 was likewise carried out both fresh and after hydrothermal oven aging on a EURO IV certified passenger vehicle with a 103 kW 2.0 l diesel engine with pump-nozzle injection system. The results are likewise reproduced in table 1.
• the four catalytically coated particulate filters were coated with different amounts of zeolites.
• the four filters F4 to F7 were produced analogously to filter F1.
• the filters were first coated homogeneously over the entire filter length with a noble metal loading of 2.12 g/l (corresponds to 60 g/ft 3 ).
• HC storage capacity of the inventive filters As a function of the zeolite content, storage tests were carried out on a 4 cylinder diesel engine with a common rail injection system (2.2 l, 100 kW). The storage tests were carried out at a constant engine operating point with a filter inlet temperature of approx. 110° C. The HC emissions upstream and downstream of the catalyst were recorded with the aid of an FID analyzer (AMA 2000, Pierburg). The storage tests were each conducted until the HC concentration downstream of the catalyst had reached a steady-state value for the duration of approx. 10 minutes. The amount of HC stored was determined from the HC concentrations upstream and downstream of the catalyst:
• the storage of hydrocarbons by the HC storage components reduces the adsorption of hydrocarbon species at the active oxidation sites of the catalyst. This also positively influences the conversion of carbon monoxide.
• the intercalation of the zeolites into the pores of the filter substrate substantially suppresses their adverse effect on the backpressure of the filter.

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• 2007
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